I have a table like this one
ID Col1 Col2 Col3
-- ---- ---- ----
1 7 NULL 12
2 2 46 NULL
3 NULL NULL NULL
4 245 1 792
I wanted a query that yields the following result
ID Col1 Col2 Col3 MIN
-- ---- ---- ---- ---
1 7 NULL 12 7
2 2 46 NULL 2
3 NULL NULL NULL NULL
4 245 1 792 1
I mean, I wanted a column containing the minimum values out of Col1, Col2, and Col 3 for each row ignoring NULL values. In a previous question (What's the best way to select the minimum value from multiple columns?) there is an answer for non NULL values. I need a query as efficient as possible for a huge table.
Select Id,
Case When Col1 < Col2 And Col1 < Col3 Then Col1
When Col2 < Col1 And Col2 < Col3 Then Col2
Else Col3
End As MIN
From YourTableNameHere
Assuming you can define some "max" value (I'll use 9999 here) that your real values will never exceed:
Select Id,
Case When Col1 < COALESCE(Col2, 9999)
And Col1 < COALESCE(Col3, 9999) Then Col1
When Col2 < COALESCE(Col1, 9999)
And Col2 < COALESCE(Col3, 9999) Then Col2
Else Col3
End As MIN
From YourTableNameHere;
You didn't specify which version of Teradata you're using. If you're using version 14+ then you can use least
.
Unfortunately least
will return null if any of its arguments are null. From the docs:
LEAST supports 1-10 numeric values. If numeric_value is the data type of the first argument, the return data type is numeric. The remaining arguments in the input list must be the same or compatible types. If either input parameter is NULL, NULL is returned.
But you can get around that by using coalesce
as Joe did in his answer.
select id,
least(coalesce(col1,9999),coalesce(col2,9999),coalesce(col3,9999))
from mytable
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